Effect levels of dietary vitamin A and zinc supplementation on performances and immunity response to foot and mouth disease viruses in swine

Effect of dietary levels of vitamin A (retinol acetate) and zinc-methionine on levels of immunities development against foot and mouth disease (FMD) viruses were examined in growing pigs. Two experiments were conducted using a total of 92 Large White pigs aged 8 weeks. Experiment 1. Relationship between levels of dietary vitamin A and zinc on serum levels of the nutrient was studied. The animals were fed diets containing 1300 IU/kg and 50 mg/kg, 3900 IU/kg and 150 mg/kg, 6500 IU/kg and 250 mg/kg of vitamin A and zinc, respectively and levels of serum vitamin A and zinc were determined at 0, 4, 8 and 12 days after feeding. It was found that levels of dietary vitamin A had no significantly (P0.05) effect on levels of serum vitamin A of the animals. However, increased levels of dietary zinc tended to increase levels of serum zinc at 12 days after the feeding. Experiment 2. The effects of levels of dietary vitamin A and zinc on performances and the development of immunities against FMD viruses type O, A and Asia I of the animals were studied. The animals were fed diets containing 1300 IU/kg and 80 mg/kg, 1300 IU/kg and 150 mg/kg, 1300 IU/kg and 200 mg/kg, 2600 IU/kg and 150 mg/kg and 3900 IU/kg and 150 mg/kg of vitamin A and zinc, respectively. Blood samples were collected at 5 periods; prevaccination, 2 weeks after the first vaccination, 2, 4 and 6 weeks after the second vaccination and subjected for determination of FMD immunity development by the method of ELISA. Increasing levels of dietary zinc significantly (P0.05) improved FCR of the animals, Elevation of dietary zinc levels also improved ADG of the animals but the differents were not significant (P0.05), However, some changes of blood characteristics have been observed in the study. Blood of pigs on diets containing increased levels of vitamin A and zinc have shown an increased content of protein as well as the non-specific immunities protein as indicated by the very rapid clotting and by the very sticking to the surface of the syringe during the blood collection. The high protein especially high non-specific immunities protein content would interfere the determination of FMD titer by ELISA method and may cause underestimation of the results.